MongoDB

MongoDB

SKILL.md

MongoDB

Description

MongoDB patterns including document design, queries, and aggregation.

When to Use

•MongoDB database operations
•Document-based data modeling
•Aggregation pipelines

Core Patterns

Document Operations

javascript

// Insert
db.users.insertOne({
  email: 'user@example.com',
  name: 'John',
  createdAt: new Date()
});

// Find
db.users.find({ active: true }).sort({ createdAt: -1 }).limit(20);

// Update
db.users.updateOne(
  { _id: ObjectId('...') },
  { $set: { name: 'Jane' } }
);

Aggregation

javascript

db.orders.aggregate([
  { $match: { status: 'completed' } },
  { $group: {
    _id: '$userId',
    totalSpent: { $sum: '$amount' },
    orderCount: { $count: {} }
  }},
  { $sort: { totalSpent: -1 } }
]);

Indexes

javascript

// Single field
db.users.createIndex({ email: 1 }, { unique: true });

// Compound
db.posts.createIndex({ userId: 1, createdAt: -1 });

Best Practices

•Embed frequently accessed data
•Use references for large/independent data
•Create indexes for query patterns
•Use aggregation for complex queries
•Avoid unbounded arrays

Common Pitfalls

•Unbounded arrays: Limit array size
•Missing indexes: Analyze query patterns
•Over-embedding: Consider data access patterns